The tetsu helm lasts for 60,000 charges of combat before degrading to nothing - it cannot be repaired. Equipping the helm will cause it to instantly degrade and become untradeable, even if it has not been used in combat.

When dying in the Wilderness or an unsafe PvP encounter, the player who kills the owner of the Tetsu helm will receive the Tetsu helm, with the same charges it had when owned by the player who was killed.